Formation of Chloroform and Other Chlorinated Byproducts by the Chlorination of Antibacterial Products

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Triclosan is a widely used antibacterial agent found in many personal hygiene products. While it has been established that pure triclosan and free chlorine readily react, interactions between triclosan-containing products and free chlorine have not previously been analyzed. Sixteen double-blinded solutions including both triclosan-containing (1.14-3.12 mg triclosan/g product) and triclosan-free products were contacted with free chlorine. Products detected included (chlorophenoxy)phenols, 2,4-dichlorophenol, 2,4,6-trichlorophenol, and chloroform. The daughter product yields were found to be highly variable and were dependent on the antimicrobial product investigated, the free chlorine to triclosan ratio, and the temperature at which the study was conducted. Lowering the temperature from 40 to 30 oC resulted in a decreased yield from 0.50 to 0.37 moles chloroform/mole triclosan after 1 minute of reaction time with [HOCl]initial = 4.0 mg/L as Cl2. Chloroform molar yields decreased to 0.29 when the initial chlorine concentration was reduced to 2.0 mg/L for a constant temperature of 40 oC. Field experiments, in which Atlanta and Danville tap waters were augmented with various soap products, exhibited differential results from the laboratory experiments in that different product yields were observed. These differences are attributed to the chlorine demand of constituents in the tap water. Higher chlorine to triclosan ratios tend to produce high levels of chloroform, while lower chlorine to triclosan ratios tend to form higher amounts of chlorophenols and (chlorophenoxy)phenol intermediates. The results from this study suggest that the chloroform produced by these reactions can be substantial under some conditions.